The wind tosses Gaby Nava's hair as the small fishing boat skims across the glassy water just off the port of Veracruz, Mexico. She smiles at the shallow bay and the Gulf of Mexico sprawling across the horizon.

"We are very lucky today. Hardly any waves. Most of the time when we come out here it's much more choppy," the marine biologist shouts over the engine roar. "It's better for Acropora palmata to be in moving waters."

When people want to see flourishing coral reefs in Mexico, they usually head for the Yucatan Peninsula, with its giant reef systems and rich fauna. They rarely think of Veracruz, the bustling shipping town on the Gulf, due east of Mexico City. Caribbean reefs, however, are becoming hard to find as the region's corals have nearly disappeared. And although Veracruz might not be a snorkeling mecca, its easily accessible reefs are the perfect place for a coral nursery.

A few kilometers into the Gulf, the boat slows as it nears a warning beacon above a massive reef that buffers the port from waves. Nava and her partners, coral specialist Miguel Roman Vives and chemist Miguel Angel-Garcia, slip on fins and masks, hop out of the boat, and kick over to a secluded spot just shy of the strongest waves, near the channel. Along the way they pass vast stretches of coral killed when the city dynamited a shipping channel after repeated ship groundings. The reefs still get hit yearly by ships, but far less than before.

Tucked between rocks and long-dead coral husks is a neat little grid of coffee-colored A. palmata, or elkhorn coral—a once-dominant species whose population plummeted in 30 years by 80 percent—growing in a bathroom-size square made of PVC tubing. The water is just a meter deep, so Nava stands up and points out several other grids, each with its own lines of corals. The corals were either collected from the many ship groundings in the area or broken off wild "seed" coral. Then they were placed on a plastic stand where they grow like tree clippings. In total, there are about 500 corals in the nursery here today, and another 3,000 that have been raised and returned to the wild on the nearby reef.

Estimates suggest that coral reefs, which cover just 2 percent of the ocean floor, support 25 percent of ocean life and feed over a billion people. In recent decades, however, coral has vanished alarmingly fast due to pollution, disease and climate change. Caribbean and Gulf waters have been hit especially hard with the extent of Caribbean coralsdeclining 80 percent, faster than that of tropical rainforests.

Over the past few decades, a small international clan of scientists, alarmed by the sudden decline of corals, have created underwater nurseries aimed at "replanting" corals to buttress wild populations. At first the effort was called quixotic and impossible, given the scale of the problem and the difficulty in raising corals. But after many trials and a few errors, coral nurseries are arising as a bona fide weapon in the fight to preserve a crucial ocean ecosystem.

Coral nurseries are a relatively new phenomenon. Whereas one or two students tinkered with the idea in the 1980s, the first serious attempts came in the mid-1990s out of marine biologist Baruch "Buki" Rinkevich's lab at the University of Haifa in Israel. It began when he went to check on some underwater fish cages in the Red Sea and noticed that a few Acropora corals had grown around them. Curious, he set up an experiment to track growth and see how many would die in a nursery over a year.

"The experiment was terminated after seven months. And the results were not based on mortality, because we had 100 percent survivorship," Rinkevich says. "We terminated it because they grew so fast that there just was no room for them."

Thus began a 15-year quest to create a viable network of coral nurseries. At first, most scientists found the whole notion crazy. Corals are notoriously fickle and slow-growing. Moreover, they have a symbiotic relationship with specific algae, the demise of either spelling death for the reef. But as many have since discovered, branching corals, especially Acropora, actually thrive in nursery environments, and their arms easily break off to form dozens or hundreds of new colonies. The new colonies not only grow faster than wild ones do, but reproduce sooner as well. Rinkevich now works with 60 species of coral in 70 localities in places such as Jamaica, Colombia, Zanzibar, Thailand and Seychelles.

"After more than 15 years, I know that it works in any reef, anywhere in the world," he says.

Few scientists today would argue that coral nurseries work. The question, however, is if they will work on a massive scale. Breaking corals into pieces is a neat trick and potentially an effective way to mitigate ship strikes, but it only really populates the immediate area. Also, every new coral is genetically identical to all the others, making the reef susceptible to disease. The real key to repopulating corals is spurring sexual reproduction. A huge cloud of gametes released from a reef can float for miles, and when it lands creates genetically new offspring.

"We're not going to restore these corals through a nursery program. The scale is just off by orders of magnitude. What we can hope to do is to set up these pockets of reproductive colonies," says marine ecologist Diego Lirman at the University of Miami. "A good sexual reproduction event will put out millions and millions of gametes into the water column. You can basically populate large areas very quickly."

The university is currently partnering with The Nature Conservancy and the National Oceanic and Atmospheric Administration for a massive coral replanting. Using $3 million in federal money, they plan to strategically plant 5,000 to 10,000 nursery-grown elkhorn corals up and down the Florida coast, each between the size of a hand and that of a soccer ball. The hope is that the effort will prove that nursery restoration can scale. In addition, the researchers will study which locations work best to grow fastest and healthiest as well as create a genetic profile to increase diversity and perhaps even connect survivorship with specific genes.

"In the case of Acropora, there is almost no way that you are ever going to recover without some kind of intervention. The population is just so fragmented," says Ken Nedimyer, an aquaculturist and former commercial fisherman among the first to begin cultivating corals in the Atlantic and is contributing a large portion of replanted colonies.

A diver for more than 35 years, Nedimyer has watched corals vanish, especially the once-ubiquitous Acropora. He says after a certain point, there were so few corals left that most only reproduced by cloning themselves. These scattered isolated groups became fodder for disease and sudden change. At his nursery, after years of crushing setbacks, Nedimyer has a diverse population with 90 different genotypes.

"We are going to have a hurricane-proof, jellyfish-proof, cold-proof, heat-proof nursery in a few years," he says ironically. Along with genetic diversity comes an ability to adapt to the changes killing corals. And although few nursery enthusiasts will admit it, most hope that somewhere in the genetic code of coral, someday they might find a strain that can withstand the effects of climate change.

Meanwhile, Rinkevich is hoping to employ a new type of nursery, seeding thousands of corals onto long ropes that quickly resemble rock candy but can be more easily pulled out and quickly moved and planted than crated corals. He admits that even at a massive scale it won't be enough to counteract the effects of pollution, overfishing and climate change. But with some luck, it might just allow a vanishing ecosystem the opportunity to pull itself back from the brink.

Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at www.springernature.com/us). Scientific American maintains a strict policy of editorial independence in reporting developments in science to our readers.